This invention relates to an improved esterification process for the oxidation products of synthetic hard paraffins.
It is a fact that esterification reactions have been the subject of substantial research. Thus, it is known to accelerate the esterification of lower fatty acids, which proceeds slowly in the absence of catalysts, by using mineral or Lewis acids. This involves a conversion of the poorly reacting cation which the nucleophilic oxygen atom of the alcohol enters into an addition with. This technique, however, becomes less effective as soon as higher fatty acids are involved, partly because of their lesser mobility, partly because the carboxyl function becomes less reactive.
On the other hand, in contrast to the esterification of lower fatty acids which with alkali form an undesirable stable carboxylate anion, the esterification of higher fatty acids with glycols can be accelerated by alkali hydroxide (Pardun, Seifen-Ole-Fett-Wachse 106, 65, 27 (1981)). Moreover, it is also known that various metal powders, oxides and salts can catalyze the esterification of fatty acids.
However, these processes cannot be applied to synthetic waxes, as has been stated in DE-AS 22 01 862 and DE-AS 24 32 215.
DE-AS 22 01 862 describes the esterification of polyethylene oxidation products with moro- or multivalent alcohols in the presence of sulphuric acid. According to its examples, however, no more than half of the waxy acids present in terms of the acid number can be esterified at 115.degree. C.; at higher temperatures undesirable discolorations have to be expected. The desired complete esterification cannot, accordingly, be attained readily; as a result the specification refers to a low esterification readiness and long reaction periods. The need for a subsequent acid neutralization is also disadvantageous.
Consequently, there remains a need to provide a solution to this longstanding technical problem.